Multi-user uplink communication using edca with polling

ABSTRACT

Simultaneous, multi-user uplink communication is scheduled in a wireless network by transmitting a poll message to a plurality of access terminals in response to receiving a first request to transmit data via uplink. The poll message includes a solicitation for requests to transmit data from each of the plurality of access terminals. The poll message also includes a medium reservation and schedule for transmission of the requests from the access terminals. Based on the requests received from the access terminals, a number of the access terminals are selected for simultaneous transmission of data via uplink. A transmit start message is sent to each of the selected access terminals indicating when and for how long the selected access terminals may transmit data via uplink. After the data is received, a block ACK message is sent to each of the selected access terminals indicating successful simultaneous communication.

CROSS-REFERENCE TO RELATED APPLICATIONS

Claim of Priority under 35 U.S.C. §119

The present Application for Patent claims priority to ProvisionalApplication No. 61/312,116, entitled “Multi-User Uplink CommunicationUsing EDCA Augmented With Polling” filed Mar. 9, 2010, and assigned tothe assignee hereof, and is hereby expressly incorporated by referenceherein in its entirety.

BACKGROUND

I. Field

The following description relates generally to communication systems,and more particularly to multiple-user uplink communication in awireless network.

II. Background

To address increasing bandwidth requirements of wireless communicationssystems, different schemes are being developed to allow multiple accessterminals to communicate with a single access point by sharing thechannel resources while achieving high data throughputs. Multiple Inputor Multiple Output (MIMO) technology represents one such approach thathas recently emerged as a popular technique for the next generationcommunication systems. MIMO technology has been adopted in severalemerging wireless communications standards such as the Institute ofElectrical and Electronics Engineers (IEEE) 802.11 standard. IEEE 802.11denotes a set of Wireless Local Area Network (WLAN) air interfacestandards developed by the IEEE 802.11 committee for short-rangecommunications (e.g., tens of meters to a few hundred meters).

In wireless communications systems, medium access (MAC) protocols aredesigned to operate to exploit several dimensions of freedom offered bythe air link medium. The most commonly exploited dimensions of freedomare time and frequency. For example, in the IEEE 802.11 MAC protocol,the “time” dimension of freedom is exploited through the CSMA (CarrierSense Multiple Access) protocol. The CSMA protocol attempts to ensurethat no more than one transmission occurs during a period of potentialhigh interference. Similarly, the “frequency” dimension of freedom canbe exploited by using different frequency channels.

Recent developments have introduced space as a dimension to be exploitedto increase, or at least more efficiently use, existing capacity.Spatial Division Multiple Access (SDMA) can improve utilization of theair link by scheduling multiple access terminals for simultaneoustransmission and reception. Data is sent to each of the terminals usingspatial streams. For example, with SDMA, a transmitter forms orthogonalstreams to individual receivers. Such orthogonal streams can be formedbecause the transmitter has several antennas and the transmit/receivechannel consists of several paths. Receivers may also have one or moreantennas (MIMO, SIMO). For this example, it is assumed that thetransmitter is an access point (AP) and the receivers are accessterminals (ATs). The streams are formed such that a stream targeted atAT-B, for example, is seen as low power interference at other accessterminals (e.g. AT-C, AT-D, . . . , etc.). Such a targeted stream willnot cause significant interference at other ATs and are likely ignored.To form these orthogonal streams, the AP needs to have channel stateinformation (CSI) from each of the receiving ATs. Although CSI can bemeasured and communicated in several ways, thereby adding complexity,the use of CSI optimizes the configuration of SDMA streams.

Additional complexities arise when MIMO is applied to multi-user (MU)systems. For example, typically, the AP controls the uplink (UL)communication process. However, in certain configurations, uplinkscheduling requires that ATs contend with the AP for channel access. Inother words, the AP will act as an additional AT trying to gain accessto the transmission medium, thereby affecting all ATs attempting to gainaccess. Further, the ability of the AP to efficiently schedule UL-SDMAtraffic depends on knowledge of the amount of uplink data available atATs to be served. Improvements to current UL scheduling schemes andmechanisms to share information useful for scheduling are desireable.

SUMMARY

According to various aspects, simultaneous, multi-user uplinkcommunication is scheduled in a wireless network by transmitting a pollmessage to a first plurality of access terminals in response toreceiving a first request to transmit data (TxR) from an accessterminal. The poll message includes a solicitation for requests totransmit data from each of the plurality of access terminals. Based onthe transmit request messages received from a second plurality of accessterminals, a number of the second plurality of access terminals areselected for assignment of a simultaneous transmit opportunity. Atransmit start message (TxS) is sent to each of the selected accessterminals indicating their assignment to the simultaneous transmitopportunity. In some examples, the TxS message indicates when and forhow long the selected access terminals may simultaneously transmit datavia uplink. After data is received from the selected access terminals inaccordance with the assignment of the simultaneous transmit opportunity,a block ACK message is transmitted to each of the selected accessterminals indicating successful simultaneous communication.

In one aspect, an access point may direct the poll message to accessterminals selected based at least in part on their participation in aprevious TxOP. For example, if an AT was regularly part of previousuplink schedules, an AP may direct the poll message to that AT. Inanother example, if the AT did not respond to a previous poll message,an AP may not direct the poll message to that AT on the assumption thatthe AT has no traffic to transmit via uplink. In another example, if theAT responded to a previous poll message, an AP may direct the pollmessage to that AT on the assumption that the AT has traffic to transmitvia uplink.

In another aspect, the poll message includes a duration field indicatinga time reservation during which transmit request messages from theaccess terminals should be received. In one example, the duration fieldincludes a value sufficient to reserve the medium for the time it willtake to complete the polling process. In this manner, communicationsfrom other access terminals will not be permitted to interfere with thepolling process. In some examples, the duration field of the pollmessage is set to a maximum backoff count.

In another aspect, the poll message includes a schedule indicating wheneach of the access terminals is to respond with a transmit requestmessage. In this manner, a mechanism exists to schedule the transmissionof the TxR messages solicited from each AT. In some examples, a fixedschedule may be communicated to each AT that separates each TxR messagein time such that there are no collisions. For example, the schedule mayindicate fixed points in time, each allocated to a particular AT. Inanother aspect, a deterministic backoff parameter may be assigned toeach AT such that the responses of each AT are sequentially ordered intime. Each AT sets their respective backoff counters to the backoffcount specified in the poll message. Each AT then contends for access tothe medium in the conventional manner using the assigned backoff count.

In another aspect, the poll message may include a specification ofpriority class or set of priority classes of data that will beconsidered for uplink communication. For example, some levels ofcommunication specified in EDCA (commonly referred to as AccessCategories) may be excluded from consideration for uplink communicationfor a particular TxOP. The limitations may be adjusted for each TxOP inany manner suitable to meet the objectives of the communication system.In this manner, the priority class of data associated with a TxR messagefrom an AT is controlled by the contents of the poll message.

In another aspect, each TxR message may indicate any of an amount ofdata for which uplink communication is requested, a priority class ofthe data for which uplink communication is requested, an amount of datain queue awaiting uplink transmission, an AT identifier, and a pollidentifier indicating that the TxR message is responsive to a particularpoll message. In addition, each TxR message may include any of trainingsymbols that AP 402 may use to estimate the uplink channel, the timerequired for the transmission, TxTime, an indication of one or morerequested durations, and a Modulation and Coding Scheme (MCS)indication.

In another aspect, an AP selects a group of access terminals for whichsimultaneous uplink communication will be allowed. The selection may bebased on any of 1) the amount of data to transmit as reported by the AT,2) the amount of data in a queue of the AT, which indicates the size ofthe queue remaining at a particular AT, 3) a priority class of the datato be transmitted, and 4) the TxOP duration requested.

In another aspect, a transmit start message (TxS) is sent to each of theselected access terminals indicating an assignment of each selected ATto the TxOP. The TxS message may include any of an indication of aspatial stream (SS) assigned to each of the selected ATs, a modulationand coding rate assignment to each of the selected ATs, a time durationfor data transmission by the selected ATs, a priority class of datapermitted to be transmitted by each of the selected ATs, power offsetvalues for each of the selected ATs, and a list of ATs allowed totransmit data in the TxOP.

In another aspect, the TxS message may include an acknowledgement of TxRmessages received by the AP, but were not selected to be served in thescheduled TxOP. In some examples, the AP stores an indication of theunserved TxR messages. After receiving data from the selected ATs inaccordance with the assignment of the first scheduled TxOP andtransmitting a block ACK message to each of the selected ATs based atleast in part on the received data, the AP contends for access to themedium and sends another TxS message to another plurality of ATs. TheTxS message indicates an assignment of another TxOP for each of the ATs,including the ATs not selected for assignment of the previouslyscheduled TxOP (i.e., the unserved TxR messages). In some otherexamples, AP 402 transmits another TxR poll, receives additional TxRmessages, and generates another TxS message that includes a transmissionopportunity for the previously unserved TxR messages.

In another aspect, a poll message is received from an AP, the pollmessage including a solicitation for a request to transmit data viauplink to the AP. A time to transmit a transmit request message to theAP is determined at least in part from a schedule indicated by the pollmessage. A transmit request message is transmitted at the determinedtime. A TxS message is received from the AP indicating an assignment ofa simultaneous transmit opportunity to transmit data via uplink to theAP. Data is transmitted via uplink to the AP in accordance with theassignment of the simultaneous transmit opportunity. A block ACK isreceived from the AP based at least in part on the transmitted data.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative aspects ofthe one or more aspects. These aspects are indicative of but a few ofthe various ways in which the principles of various aspects may beemployed and the described aspects are intended to include all suchaspects and their equivalents

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a wireless communications network configured inaccordance with an aspect of the disclosure;

FIG. 2 is a wireless node that includes a front end processing system ina wireless node in the wireless communications network of FIG. 1;

FIG. 3 is a timing diagram illustrating the operation of a traditionalAccess Point (AP)-initiated UL SDMA frame sequence;

FIG. 4 is a timing diagram illustrating the operation of an accessterminal/client-initiated UL SDMA scheme configured in accordance withone aspect of the disclosure;

FIG. 5 is a flow diagram illustrating the operation of the accessterminal/client-initiated UL SDMA scheme of FIG. 4 configured inaccordance with one aspect of the disclosure;

FIG. 6 is a flow diagram illustrating the operation of the accessterminal/client-initiated UL SDMA scheme configured in accordance withanother aspect of the disclosure;

FIG. 7 is a flow diagram illustrating the operation of theAT/client-initiated UL SDMA scheme configured in accordance with anotheraspect of the disclosure;

FIG. 8 is a block diagram illustrating the functionality of an accesspoint apparatus for implementing a client-initiated UL scheme with aplurality of ATs in accordance with one aspect of the disclosure.

FIG. 9 is a block diagram illustrating the functionality of an ATapparatus for implementing a client-initiated UL scheme for a pluralityof ATs in accordance with one aspect of the disclosure; and

FIG. 10 is a block diagram of an apparatus that includes a processingsystem.

DETAILED DESCRIPTION

Various aspects of the novel systems, apparatus and methods aredescribed more fully hereinafter with reference to the accompanyingdrawings. The teachings of this disclosure may, however, be embodied inmany different forms and should not be construed as limited to anyspecific structure or function presented throughout this disclosure.Based on the teachings herein one skilled in the art should appreciatethat that the scope of disclosure is intended to cover any aspect of thesystems, apparatus and methods disclosed herein, whether implementedindependently of or combined with any other aspect of the disclosure.For example, an apparatus may be implemented or a method may bepracticed using any number of the aspects set forth herein. In addition,the scope of the disclosure is intended to cover such an apparatus ormethod which is practiced using other structure, functionality, orstructure and functionality in addition to or other than the variousaspects of the disclosure set forth herein. It should be understood thatany aspect disclosed herein may be embodied by one or more elements of aclaim.

Several aspects of a wireless network will now be presented withreference to FIG. 1. The wireless network, which is also referred toherein as a basic service set (BSS) 100 is shown with several wirelessnodes, generally designated as an access point 110 and a plurality ofaccess terminals (ATs) or stations (STAs) 120. Each wireless node iscapable of receiving and/or transmitting. In the detailed descriptionthat follows, the term “access point” is used to designate atransmitting node and the term “access terminal” is used to designate areceiving node for downlink communications, whereas the term “accesspoint” is used to designate a receiving node and the term “accessterminal” is used to designate a transmitting node for uplinkcommunications. However, those skilled in the art will readilyunderstand that other terminology or nomenclature may be used for anaccess point and/or access terminal. By way of example, an access pointmay be referred to as a base station, a base transceiver station, astation, a terminal, a node, a wireless node, an access terminal actingas an access point, or some other suitable terminology. An accessterminal may be referred to as a user terminal, a mobile station, asubscriber station, a station, a wireless device, a terminal, a node, awireless node or some other suitable terminology. The various conceptsdescribed throughout this disclosure are intended to apply to allsuitable wireless nodes regardless of their specific nomenclature.

The wireless network 100 may support any number of access pointsdistributed throughout a geographic region to provide coverage foraccess terminals 120. As depicted, access terminals 120 may be spatiallyseparated. A system controller 130 may be used to provide coordinationand control of the access points, as well as access to other networks(e.g., Internet) for the access terminals 120. For simplicity, oneaccess point 110 is shown. An access point is generally a fixed terminalthat provides backhaul services to access terminals in the geographicregion of coverage. However, the access point may be mobile in someapplications. An access terminal, which may be fixed or mobile, utilizesthe backhaul services of an access point or engages in peer-to-peercommunications with other access terminals. Examples of access terminalsinclude a telephone (e.g., cellular telephone), a laptop computer, adesktop computer, a Personal Digital Assistant (PDA), a digital audioplayer (e.g., MP3 player), a camera, a game console, or any othersuitable wireless node.

The wireless network 100 may support MIMO technology. Using MIMOtechnology, an access point 110 may communicate with multiple accessterminals 120 simultaneously using Spatial Division Multiple Access(SDMA). SDMA is a multiple access scheme that enables multiple streamssharing the same frequency channel to be simultaneously transmitted todifferent receivers. This provides higher user capacity. This isachieved by spatially precoding each data stream and then transmittingeach spatially precoded stream through a different transmit antenna onthe downlink. The spatially precoded data streams arrive at the accessterminals with different spatial signatures, which enables each accessterminal 120 to recover the data stream destined for that accessterminal 120. On the uplink, each access terminal 120 transmits aspatially precoded data stream, which enables the access point 110 toidentify the source of each spatially precoded data stream. It should benoted that although the term “precoding” is used herein, in general, theterm “coding” may also be used to encompass the process of precoding,encoding, decoding and/or postcoding a data stream.

One or more access terminals 120 may be equipped with multiple antennasto enable certain functionality. In this configuration, for example,multiple antennas at an access terminal 120 may be used to communicatewith a multiple antenna access point 110 to improve data throughputwithout additional bandwidth or transmit power. This may be achieved bysplitting a high data rate signal at the transmitter into multiple lowerrate data streams with different spatial signatures, thus enabling thereceiver to separate these streams into multiple channels and properlycombine the streams to recover the high rate data signal.

While portions of the following disclosure describe access terminalsthat support MIMO technology, the access point 110 may also beconfigured to support access terminals that do not support MIMOtechnology. This approach may allow older versions of access terminals(i.e., “legacy” terminals) to remain deployed in a wireless network,extending their useful lifetime, while allowing newer MIMO accessterminals to be introduced as appropriate.

In the detailed description that follows, various aspects of thedisclosure will be described with reference to a MIMO system supportingany suitable wireless technology, such as Orthogonal Frequency DivisionMultiplexing (OFDM). OFDM is a spread-spectrum technique thatdistributes data over a number of subcarriers spaced apart at precisefrequencies. The spacing provides “orthogonality” that enables areceiver to recover the data from the subcarriers. An OFDM system mayimplement IEEE 802.11, or some other air interface standard. Othersuitable wireless technologies include, by way of example, Code DivisionMultiple Access (CDMA), Time Division Multiple Access (TDMA), or anyother suitable wireless technology, or any combination of suitablewireless technologies. A CDMA system may implement IS-2000, IS-95,IS-856, Wideband-CDMA (WCDMA), or some other suitable air interfacestandard. A TDMA system may implement Global System for MobileCommunications (GSM) or some other suitable air interface standard. Asthose skilled in the art will readily appreciate, the various aspects ofthis disclosure are not limited to any particular wireless technologyand/or air interface standard.

The wireless node, whether an access point or access terminal, may beimplemented with a protocol that utilizes a layered structure thatincludes a physical (PHY) layer that implements all the physical andelectrical specifications to interface the wireless node to the sharedwireless channel, a Medium Access Control (MAC) layer that coordinatesaccess to the shared wireless channel, and an application layer thatperforms various data processing functions including, by way of example,speech and multimedia codecs and graphics processing. Additionalprotocol layers (e.g., network layer, transport layer) may be requiredfor any particular application. In some configurations, the wirelessnode may act as a relay point between an access point and accessterminal, or two access terminals, and therefore, may not require anapplication layer. Those skilled in the art will be readily able toimplement the appropriate protocol for any wireless node depending onthe particular application and the overall design constraints imposed onthe overall system.

When the wireless node in a transmit mode, the application layerprocesses data, segments the data into packets, and provides the datapackets to the MAC layer. The MAC layer assembles MAC packets with eachdata packet from the application layer being carried by the payload of aMAC packet. Alternatively, the payload for a MAC packet may carry afragment of a data packet or multiple data packets from the applicationlayer. Each MAC packet includes a MAC header and an error detectioncode. The MAC packet is sometimes referred to as a MAC Protocol DataUnit (MPDU), but may also be referred to as a frame, packet, timeslot,segment, or any other suitable nomenclature.

When the MAC layer decides to transmit, it provides a block of MACpackets to the PHY layer. The PHY layer assembles a PHY packet byassembling the block of MAC packets into a payload and adding apreamble. The PHY layer is also responsible for providing various signalprocessing functions (e.g., modulating, coding, spatial processing,etc.). The preamble, which is sometimes referred to as Physical LayerConvergence Protocol (PLCP), is used by the receiving node to detect thestart of the PHY packet and synchronize to the transmitter's node dataclock. The PHY packet is sometimes referred to as a Physical LayerProtocol Data Unit (PLPDU), but may also be referred to as a frame,packet, timeslot, segment, or any other suitable nomenclature.

When the wireless node is in a receive mode, the process is reversed.That is, the PHY layer detects an incoming PHY packet from the wirelesschannel. The preamble allows the PHY layer to lock in on the PHY packetand perform various signal processing functions (e.g., demodulating,decoding, spatial processing, etc.). Once processed, the PHY layerrecovers the block of MAC packets carried in the payload of the PHYpacket and provides the MAC packets to the MAC layer. The MAC layerchecks the error detection code for each MAC packet to determine whetherit was successfully decoded. If the error detection code for a MACpacket indicates that it was successfully decoded, then the payload forthe MAC packet is provided to the application layer. If the errordetection code for a MAC packet indicates that it was unsuccessfullydecoded, the MAC packet is discarded. A Block Acknowledgement (BA) maybe sent back to the transmitting node indicating which data packets weresuccessfully decoded. The transmitting node uses the BA to determinewhich data packets, if any, require retransmission.

FIG. 2 is a conceptual block diagram illustrating an example of thesignal processing functions of the PHY layer that may be executed by anyof AP 110 and AT 120 illustrated in FIG. 1. In a transmit mode, a TXdata processor 202 may be used to receive data from the MAC layer andencode (e.g., Turbo code) the data to facilitate Forward ErrorCorrection (FEC) at the receiving node. The encoding process results ina sequence of code symbols that that may be blocked together and mappedto a signal constellation by the TX data processor 202 to produce asequence of modulation symbols.

The modulation symbols from the TX data processor 202 may be provided toa TX spatial processor 204. TX spatial processor 204 performs spatialprocessing of the modulation symbols. This may be accomplished byspatial precoding the modulation symbols. In wireless nodes implementingOFDM, the spatially precoded modulation symbols are provided to an OFDMmodulator 206. OFDM modulator 206 splits the modulation symbols intoparallel streams. Each stream is then mapped to an OFDM subcarrier andthen combined using an Inverse Fast Fourier Transform (IFFT) to producea time domain OFDM stream. Each spatially precoded OFDM stream is thenprovided to a different antenna 210 a-210 n via a respective transceiver208 a-208 n. Each transceiver 208 a-208 n modulates an RF carrier with arespective precoded stream for transmission over the wireless channel.

In a receive mode, each transceiver 208 a-208 n receives a signalthrough its respective antenna 210 a-210 n. Each transceiver 208 a-208 nmay be used to recover the information modulated onto an RF carrier. Inwireless nodes implementing OFDM, each transceiver 208 a-208 n mayprovide the information to an OFDM demodulator 220. The OFDM demodulator220 converts the stream (or combined stream) from time-domain to thefrequency domain using a Fast Fourier Transform (FFT). The frequencydomain signal comprises a separate stream for each subcarrier of theOFDM signal. The OFDM demodulator 220 recovers the data (i.e.,modulation symbols) carried on each subcarrier and multiplexes the datainto a stream of modulation symbols before sending the stream to a RXspatial processor 222. RX spatial processor 222 performs spatialprocessing on the information to recover any spatial streams destinedfor the wireless node 200. The spatial processing may be performed inaccordance with Channel Correlation Matrix Inversion (CCMI), MinimumMean Square Error (MMSE), Soft Interference Cancellation (SIC), or someother suitable technique. If multiple spatial streams are destined forthe wireless node 200, they may be combined by the RX spatial processor222. RX data processor 224 may be used to translate the modulationsymbols back to the correct point in the signal constellation. Becauseof noise and other disturbances in the wireless channel, the modulationsymbols may not correspond to an exact location of a point in theoriginal signal constellation. The RX data processor 224 detects whichmodulation symbol was most likely transmitted by finding the smallestdistance between the received point and the location of a valid symbolin the signal constellation. These soft decisions may be used, in thecase of Turbo codes, for example, to compute a Log-Likelihood Ratio(LLR) of the code symbols associated with the given modulation symbols.The RX data processor 224 then uses the sequence of code symbol LLRsdecode the data that was originally transmitted before providing thedata to the MAC layer.

In some embodiments, wireless node 200 includes processing system 1000operable to perform simultaneous, multi-user uplink communication in awireless network in accordance with the various examples and embodimentspresented herein.

FIG. 3 illustrates a timing diagram 300 that illustrates a traditionalsequence for AP-initiated uplink SDMA transmission by an AP 302 with aplurality of ATs 310-1 to 310-3 in one example. The AP 302 gains accessto the medium using Enhanced Distributed Channel Access (EDCA). Accessis provided based on a priority depending on an uplink traffic AccessCategory (AC) from the plurality of ATs 310-1 to 310-3. The AP 302 thensends out a Request SDMA (RSDMA) message 304, requesting clients such asthe plurality of ATs 310-1 to 310-3 to send an UL Request ToSend-Multiple Access (RTS-MA) message. UL RTS-MA messages aretransmitted using pre-assigned time-slots and spatial streams (SS),where the assignment is performed by the AP 302. The plurality of ATs310-1 to 310-3 respond with respective RTS-MA messages 312-1 to 312-3.Each RTS-MA message contains UL traffic AC, an EDCA backoff countervalue and a packet size. The AP 302 may optionally send an RTS-MA-ACK(RMA) message 306, acknowledging the RTS-MA messages 312-1 to 312-3 andrequesting sounding for UL SDMA modulation and coding scheme (MCS)calculation purposes. The AP 302 then sends an RTS-MA Confirmation (RMC)message 308 with SS, MCS and any power offset values required for ULSDMA for selected clients. These clients are selected to preserve theirEDCA priorities (backoff counter value and AC). The RMC message 308 alsoreserves the medium for a time period needed to perform a transmissionoperation, referred to as a TxOP duration. The TxOP duration can bebased on longest packet size requested by the selected clients. Clientsthen send UL SDMA packets; illustrated as SDMA data transmissions 316-1to 316-3, using the SS, MCS and power offset values as suggested by theAP 302. Once the AP 302 has successfully received the UL SDMA packets,the AP 302 responds with a Block ACK (BA) message 320 to acknowledge thetransmission from the clients. After a successful transmission of the ULSDMA packets, the clients may re-initialize their backoff counters forEDCA access. In some examples, the clients may prefer to not use EDCAaccess for UL traffic and rely on scheduled RSDMA or RTS-MA-Confirmationmessages for future UL transmissions.

The above-described AP initiated UL-SDMA scheme can encounter issues insome scenarios. In one example, if the clients re-initialize theirbackoff counters for EDCA access after UL-SDMA transmission, the AP maystill contend for the medium on behalf of other clients that need tosend UL traffic even if the AP has no traffic to send. This results inthe AP also competing with these clients for medium access. In otherwords, the AP will act as a “virtual AT”. With overlapping basicservices sets (OBSS), the number of these “virtual ATs” will increase inthe network and lead to an increased number of collisions.

Issues may arise if the clients rely purely on scheduled RSDMA or RMCmessages from the AP for scheduling future UL transmission. For example,scheduled access works well for fixed rate traffic such as video orvoice over Internet Protocol (VoIP) traffic, but does not extend well tobursty data traffic. In another example, the reliance on AP schedulingmessages by the clients in the presence of OBSS with several APs willlead to increased collisions of scheduled RSDMAs. This can be mitigatedto some extent, but not completely, using random backoff values. Inanother example, the AP design is complicated when the AP is solelyresponsible for scheduling UL SDMA transmissions.

In a client-initiated transmission process, the AP is not aware of thebuffer status of the ATs and consequently, the AP does not know which ofthe ATs need to send data. To address this, the AP may send a pollmessage (TxR poll) that includes a solicitation for transmit requestmessages (TxRs) from a number of ATs. In response, the ATs may each senda TxR message to the AP indicating that they want to send data. Inresponse, the AP may grant a transmission opportunity (TxOP) to the ATsby sending a transmit start (TxS) message to selected ATs.

A client initiated SDMA uplink reservation protocol between an AP 402and a plurality of access terminals (e.g., AT-1 401 to AT-5 406) will bedescribed with reference to a timing diagram 400 as illustrated in FIG.4, and further with reference to a client initiated UL SDMA process 500as illustrated by FIG. 5.

At block 510, an AT-1 401 gains access to the medium using EDCA andsends a transmit request message (TxR) 410 to the AP 402. The TxRmessage 410 may indicate a priority class specification of data to betransmitted. TxR message 410 may include an identifier of AT-1 401. TxRmessage 410 may also include an amount of data that AT-1 401 wants totransmit via uplink. In addition, TxR message 410 may also includetraining symbols that AP 402 may use to estimate the uplink channel. TheTxR message 410 may also include the time required for the transmission,TxTime. A request from an AT may include an indication of one or morerequested durations, where each requested duration is referred to apossible SDMA transmission setting, such as the total number of spatialstreams. Each request from an AT may also include a Modulation andCoding Scheme (MCS) indication, referring to the MCS that the AT will beusing in relation with the requested transmission duration. From theduration and the requested MCS, the AP may determine the amount of datathe AT needs to send.

At block 520, in one aspect of the disclosure, the AP 402 responds toTxR message 410 with a poll message 411 that includes a solicitation fortransmit request messages (TxRs) from several access terminals. Fouraccess terminals (AT-2 403 to AT-5 406) are illustrated in FIG. 4 forexemplary purposes. However, any number of access terminals may becontemplated. In some examples, poll message 411 may be targeted toapproximately ten access terminals. In some examples, poll message 411may be broadcast to many more access terminals. However, in such cases,the broadcast message includes the destination addresses of only theaccess terminals for which the poll message is intended. In otherexamples, poll message 411 may be individually transmitted to each ofthe desired access terminals. In many examples, AP 402 directs the pollmessage 411 to a limited number of access terminals within range toavoid wasteful consumption of available resources. AP 402 may selectaccess terminals to direct the poll message 411 based on any of severalfactors including the history of previous communications between the APand the AT. In one aspect, an access point may direct the poll messageto access terminals selected based at least in part on theirparticipation in a previous TxOP. For example, if an AT was regularlypart of previous uplink schedules, an AP may direct the poll message tothat AT. In another example, if the AT did not respond to a previouspoll message, an AP may not direct the poll message to that AT on theassumption that the AT has no traffic to transmit via uplink. In anotherexample, if the AT responded to a previous poll message, an AP maydirect the poll message to that AT on the assumption that the AT hastraffic to transmit via uplink.

In one aspect, the poll message includes a duration field indicating atime reservation during which transmit request messages from the accessterminals should be received. In one example, poll message 411 includesa duration field with a value sufficient to reserve the medium for thetime it will take to complete the polling process. In this manner,communications from other access terminals will not be permitted tointerfere with the polling process. In one example, AP 402 sets theduration field of poll message 411 to encompass a maximum backoff count.In this example, the duration field of the poll message 411 is set to(MaxBackoffCount×slot time). By way of example, the value of slot timein 802.11/a/n/ac is nine microseconds. MaxBackoffCount is specified tobe at least the largest backoff count value assigned to any of the ATssolicited by the AP 402 in poll message 411. By assignment of theduration field of the poll message 411 to the maximum amount of timerequired to receive a TxR message from each of the solicited ATs, themedium is effectively reserved for the polling process because nodesthat are not polled are prevented from accessing the medium during thistime.

In another aspect, poll message 411 includes a mechanism to schedule thetransmission of the TxR messages solicited from each AT. In someexamples, a fixed schedule in time may be constructed by AP 402 andcommunicated to each AT. In this manner, the TxR message transmittedfrom each AT is coordinated in time such that there are no collisions.In other examples, a deterministic backoff parameter may be assigned toeach AT by AP 402 such that the responses of each AT are sequentiallyordered in time. This approach may save time by allowing an AT to stepin place of an AT that does not send a TxR message without waiting forthe entire duration of time allocated to a TxR message to elapse with notransmission. If the poll message includes deterministic backoffparameters assigned to each solicited AT, the ordering of the TxRmessages from each of the ATs is based on the assigned backoffparameters. In one example, as discussed above, AP 402 sets the durationfield of poll message 411 to encompass the maximum backoff count. Inthis example, the duration field of the poll message 411 is set to(MaxBackoffCount×slot_time). When soliciting four access terminals,MaxBackoffCount may be four. When an access terminal transmits a TxRmessage, it sets the duration field of the TxR message to(MaxBackoffCount−ATBackoffCount)×slot time). ATBackoffCount is thedeterministic backoff count value assigned by AP 402 to each AT in pollmessage 411. For example, AT-5 406 may be assigned a ATBackoffCountvalue of four, AT-4 405 may be assigned a ATBackoffCount value of three,etc. Each AT sets their respective backoff counters to the backoff countspecified in poll message 411. Each AT then contends for access to themedium in the conventional manner using the assigned backoff count. Inthis manner, the order of TxR messages is determined by the assignmentof a different ATBackoffCount value for each AT and a lapse incommunication of a TxR message from one AT can be filled by asubsequently scheduled AT.

In another aspect, the poll message 411 may include a priority classspecification or set of priority class specifications of data that willbe considered by AP 402 for uplink communication in the upcoming TxOP.For example, some priority classes of communication specified in EDCA(commonly referred to as Access Categories) may be excluded fromconsideration for uplink communication for a particular TxOP byexcluding them from the set of priority class specifications included inpoll message 411. In one example, a priority class of data to betransmitted from an access terminal must match the priority classspecification for an access terminal to be considered for assignment ofa TxOP. In another example, a priority class of data to be transmittedfrom an access terminal must either match or exceed the priority classspecification for an access terminal to be considered for assignment ofa TxOP. The limitations may be adjusted for each TxOP in any mannersuitable to meet the objectives of the communication system. In thismanner, the priority class of data associated with a TxR message from anAT is controlled by the AP 402 via poll message 411.

At block 540, in one aspect of the disclosure, each of AT-2 403, AT-3404, and AT-5 406 transmit TxR messages 412, 413, and 415, respectivelyto AP 402 in response to poll message 411. In various examples, each ofTxR messages 412, 413, and 415 may indicate any of 1) an amount of datafor which uplink communication is requested, 2) a priority class of thedata for which uplink communication is requested, 3) an amount of datain queue awaiting uplink transmission, 4) a station identifier, and 5) apoll identifier indicating that the TxR message is responsive to aparticular poll message (e.g., poll message 411). In other examples, TxRmessages 412, 413, and 415 may include any of 1) training symbols thatAP 402 may use to estimate the uplink channel, 2) the time required forthe transmission, TxTime, 3) an indication of one or more requesteddurations, where each duration is referred to a possible SDMAtransmission setting, such as the total number of spatial streams, and4) a Modulation and Coding Scheme (MCS) indication, referring to the MCSthat the AT will be using with the requested transmission duration. Fromthe duration and the requested MCS, the AP may determine the amount ofdata the AT needs to send.

In the example depicted in FIG. 4, AT-4 405 sends a message 414 to AP405 indicating that it does not make a request for uplink transmissionof data. For example, AT-4 405 may have no data it wishes to transmit toAP 402. As depicted, such an indication may be communicated by explicitmessage 414. In other examples, AT-4 405 may simply not respond to pollmessage 411.

After receiving TxR messages 412, 413, and 415, at block 550, the AP 402selects a group of access terminals for which uplink communication willbe allowed. In some examples, all of the access terminals (e.g. all ofterminals AT-1, AT-2, AT-3, and AT-5) that respond with a TxR messageare selected for participation in a transmit opportunity (TxOP). In someother examples, only a subset of the access terminals that respond witha TxR message are selected for participation in the TxOP. As depicted inFIG. 4, terminals AT-1 417, AT-2 418, and AT-3 419 are selected for TxOP425. The determination of the participants in the TxOP may be based onany of 1) the amount of data to transmit as reported by the AT, 2) theamount of data in a queue (e.g. queue size) of the AT, which indicatesthe size of the queue remaining at a particular AT, 3) a priority classof the data to be transmitted, and 4) the TxOP duration requested (e.g.,TxTime).

At block 560, a transmit start message (TxS) 416 is sent to each of theselected access terminals indicating an assignment of each selected ATto the TxOP. In one example, TxS message 416 acts as a clear to send(CTS) message to AT-1 401, AT-2 403, and AT-3 404, and reserves themedium for a TxOP 425 of maximum time duration TxTime specified by AP402. The AP 402 also may also assign spatial stream (SS), modulation andcoding values, and power offset values, the assignment of which areoptional, for each of AT-1 401, AT-2 403, and AT-3 404 to send UL-SDMAtraffic within the TxOP 425. The TxS message 416 may carry a list of ATsallowed to transmit data in the UL-SDMA TxOP, the maximum duration ofthe data transmission (TxTime), the power level adjustment for each AT,which may be defined based on the stored power from the received TxRmessage, the total number of spatial streams allocated, a time offset tocorrect packet transmission start time, as well as an MCS indication perAT or an MCS backoff indication per AT. At block 570, data issimultaneously transmitted from each selected access terminal to AP 402during a TxOP associated with each access terminal. As depicted in FIG.4, data 417-419 is simultaneously transmitted from AT-1, AT-2, and AT-3,respectively, to AP 402 during TxOP 425. At block 580, aftersuccessfully receiving data 417-419 simultaneously transmitted duringthe uplink data TxOP 425, a block acknowledgement (ACK) message 421-423is sent to each served access terminal. As depicted in FIG. 4, AP 402transmits block ACK messages 421-423 to AT-1 401, AT-2 403, and AT-3404, respectively.

In another aspect, the TxS message 416 may include an acknowledgement ofTxR messages received by AP 402 that were not selected to be served inthe scheduled TxOP. As depicted in FIG. 4, in some examples, AP 402stores an indication of the unserved TxR messages 427 in a memory (e.g.,memory 1006). In some examples, upon completing the data reception andtransmission of the block ACKs 421-423, AP 402 contends for access tothe medium and sends another TxS message 424 that includes a TxOP 426for the unserved TxR messages (e.g., TxR message 415). In some otherexamples, AP 402 transmits another TxR poll, receives additional TxRmessages, and generates a TxS message that includes a transmissionopportunity for both the previously unserved TxR messages and at leastsome of the additional TxR messages.

FIG. 6 illustrates an alternative set of blocks 530 to those depicted inFIG. 5. In the alternative approach, after poll message 411 istransmitted, each TxR message is sequentially received (block 610) andconsidered for participation in a TxOP. At block 620, AP 402 maydetermine that no more TxR messages will be considered and terminate therequest for TxR messages. For example, AP 402 may receive several TxRmessages and then run out of capacity to accommodate the requests (e.g.,number of spatial streams allocated reaches the number of antennas at AP402). In this case, rather than continuing to receive TxR messageswithout being able to assign them a TxOP, AP 402 elects to stopreceiving TxR messages. In this manner, AP 402 can proceed to send a TxSmessage without further delay.

The proposed client initiated SDMA uplink reservation protocol betweenan AP 402 and an access terminal (e.g., AT-2 403) is also described withreference to client initiated UL SDMA process 700 as illustrated by FIG.7 and with further reference to the timing diagram of FIG. 4.

At block 710, an access terminal (e.g., AT-2 403) receives a pollmessage 411 from AP 402 including a solicitation for a transmit requestmessage (TxR) from AT-2 403 and soliciting TxR messages from otheraccess terminals (e.g. AT-3 404 to AT-5 406) as discussed in furtherdetail herein.

At block 720, AT-2 403 determines an ordering of the TxR messagessolicited by AP 402. If the poll message includes a fixed time schedule,AT-2 403 determines the ordering of the TxR messages based on the timeappointed to AT-2 403 in the poll message. If the poll message includesa deterministic backoff parameter assigned to AT-2 403, the ordering ofthe TxR messages is based on the order of the assigned backoffparameters as discussed in further detail above.

At block 730, AT-2 403 sends a TxR message 412 in accordance with theordering determined at block 720. In various examples, TxR message 412may indicate any of an amount of data for which uplink communication isrequested, a priority class of the data for which uplink communicationis requested, an amount of data in queue awaiting uplink transmission, astation identifier, and a poll identifier indicating that the TxRmessage is responsive to a particular poll message (e.g., poll message411). In other examples, TxR message 412 may include any of trainingsymbols that AP 402 may use to estimate the uplink channel, the timerequired for the transmission, TxTime, an indication of one or morerequested durations, where each duration is referred to a possible SDMAtransmission setting, such as the total number of spatial streams, and aModulation and Coding Scheme (MCS) indication, referring to the MCS thatthe AT will be using with the requested transmission duration. From theduration and the requested MCS, the AP may determine the amount of datathe AT needs to send.

At block 740, AT-2 403 receives a TxS message 416 indicating anassignment of a TxOP 425 to AT-2 403. In one example, TxS message 416acts as a clear to send (CTS) message to AT-2 403 and reserves themedium for a TxOP 425 of maximum time duration TxTime specified by AP402. The AP 402 also may also assign spatial stream (SS), modulation andcoding values, and power offset values, the assignment of which areoptional, for AT-2 403 to send UL-SDMA traffic within the TxOP 425. TheTxS message 416 may carry a list of ATs allowed to transmit data in theUL-SDMA TxOP, the maximum duration of the data transmission (TxTime),the power level adjustment for each AT, which may be defined based onthe stored power from the received TxR message, the total number ofspatial streams allocated, a time offset to correct packet transmissionstart time, as well as an MCS indication per AT or an MCS backoffindication per AT. At block 750, AT-2 403 sends data 418 to AP 402during the TxOP 425 assigned to AT-2 403 by AP 402 and communicated toAT-2 403 in TxS message 416. Data 418 is transmitted by AT-2 403 at thesame time as data 417 is transmitted by AT-1 401 and data 419 istransmitted by AT-3 404.

FIG. 8 is a diagram illustrating the functionality of an access pointapparatus 800 in accordance with one aspect of the disclosure. Theapparatus 800 includes a poll message transmit module 802 fortransmitting a poll message to a plurality of wireless nodes solicitingrequests to transmit via uplink; a wireless node selection module 804for selecting a group of wireless nodes to be assigned a transmissionopportunity based at least in part on requests to transmit received inresponse to the poll message; and a data receive module 806 forsimultaneously receiving data from the wireless nodes during theassigned transmission opportunity.

FIG. 9 is a diagram illustrating the functionality of an access terminalapparatus 900 in accordance with one aspect of the disclosure. Theapparatus 900 includes a poll message receive module 902 for receiving apoll message including a solicitation for a request to transmit data viauplink; a transmit start receive module 904 for receiving a transmitstart message indicating an assignment of a simultaneous transmitopportunity; and a data transmit module 906 for simultaneouslytransmitting data via uplink in accordance with the simultaneoustransmit opportunity.

FIG. 10 illustrates an example of a hardware configuration for aprocessing system 1000 in a wireless node (e.g., AP 110 and AT 120). Inthis example, the processing system 1000 may be implemented with a busarchitecture represented generally by bus 1002. The bus 1002 may includeany number of interconnecting buses and bridges depending on thespecific application of the processing system 1000 and the overalldesign constraints. The bus links together various circuits including aprocessor 1004, computer-readable media 1006, and a bus interface 1008.The bus interface 1008 may be used to connect a network adapter 1010,among other things, to the processing system 1000 via the bus 1002. Thenetwork interface 1010 may be used to implement the signal processingfunctions of the PHY layer. In the case of an access terminal 120 (seeFIG. 1), a user interface 1012 (e.g., keypad, display, mouse, joystick,etc.) may also be connected to the bus via the bus interface 1008. Thebus 1002 may also link various other circuits such as timing sources,peripherals, voltage regulators, power management circuits, and thelike, which are well known in the art, and therefore, will not bedescribed any further.

The processor 1004 is responsible for managing the bus and generalprocessing, including the execution of software stored on thecomputer-readable media 1006. In some embodiments, computer-readablemedium 1006 may store computer executable codes such that when the codesare executed by a computer cause the computer to perform the functionsdescribed herein. The processor 1004 may be implemented with one or moregeneral-purpose and/or special purpose processors. Examples includemicroprocessors, microcontrollers, digital signal processors (DSPs),field programmable gate arrays (FPGAs), programmable logic devices(PLDs), state machines, gated logic, discrete hardware circuits, andother suitable hardware configured to perform the various functionalitydescribed throughout this disclosure.

One or more processors in the processing system may execute software.Software shall be construed broadly to mean instructions, instructionsets, code, code segments, program code, programs, subprograms, softwaremodules, applications, software applications, software packages,routines, subroutines, objects, executables, threads of execution,procedures, functions, etc., whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.

The software may reside on a computer-readable medium. Acomputer-readable medium may include, by way of example, a magneticstorage device (e.g., hard disk, floppy disk, magnetic strip), anoptical disk (e.g., compact disk (CD), digital versatile disk (DVD)), asmart card, a flash memory device (e.g., card, stick, key drive), randomaccess memory (RAM), read only memory (ROM), programmable ROM (PROM),erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register,a removable disk, a carrier wave, a transmission line, or any othersuitable medium for storing or transmitting software. Thecomputer-readable medium may be resident in the processing system,external to the processing system, or distributed across multipleentities including the processing system. Computer-readable medium maybe embodied in a computer-program product. By way of example, acomputer-program product may include a computer-readable medium inpackaging materials.

In the hardware implementation illustrated in FIG. 10, thecomputer-readable media 1006 is shown as part of the processing system1000 separate from the processor 1004. However, as those skilled in theart will readily appreciate, the computer-readable media 1006, or anyportion thereof, may be external to the processing system 1000. By wayof example, the computer-readable media 1006 may include a transmissionline, a carrier wave modulated by data, and/or a computer productseparate from the wireless node, all which may be accessed by theprocessor 1004 through the bus interface 1008. Alternatively, or inaddition to, the computer readable media 1006, or any portion thereof,may be integrated into the processor 1004, such as the case may be withcache and/or general register files.

Those of skill will appreciate that any of the various illustrativelogical blocks, modules, processors, means, circuits, and algorithmsteps described in connection with the aspects disclosed herein may beimplemented as electronic hardware (e.g., a digital implementation, ananalog implementation, or a combination of the two, which may bedesigned using source coding or some other technique), various forms ofprogram or design code incorporating instructions (which may be referredto herein, for convenience, as “software” or a “software module”), orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

By way of example, several aspects of telecommunication systems havebeen presented with reference to various apparatus and methods. Theseapparatus and methods have been described herein and illustrated in theaccompanying drawing by various blocks, modules, components, circuits,steps, processes, algorithms, etc. (collectively referred to as“elements”). These elements may be implemented using electronichardware, computer software, or any combination thereof. Whether suchelements are implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem.

Further by way of example, an element, or any portion of an element, orany combination of elements may be implemented with a “processingsystem” that includes one or more processors. Examples of processorsinclude microprocessors, microcontrollers, digital signal processors(DSPs), field programmable gate arrays (FPGAs), programmable logicdevices (PLDs), state machines, gated logic, discrete hardware circuits,and other suitable hardware configured to perform the variousfunctionality described throughout this disclosure. One or moreprocessors in the processing system may execute software. Software shallbe construed broadly to mean instructions, instruction sets, code, codesegments, program code, programs, subprograms, software modules,applications, software applications, software packages, routines,subroutines, objects, executables, threads of execution, procedures,functions, etc., whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise. The software mayreside on a computer-readable medium. A computer-readable medium mayinclude, by way of example, a magnetic storage device (e.g., hard disk,floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD),digital versatile disk (DVD)), a smart card, a flash memory device(e.g., card, stick, key drive), random access memory (RAM), read onlymemory (ROM), programmable ROM (PROM), erasable PROM (EPROM),electrically erasable PROM (EEPROM), a register, a removable disk, acarrier wave, a transmission line, or any other suitable medium forstoring or transmitting software. The computer-readable medium may beresident in the processing system, external to the processing system, ordistributed across multiple entities including the processing system.Computer-readable medium may be embodied in a computer-program product.By way of example, a computer-program product may include acomputer-readable medium in packaging materials. Those skilled in theart will recognize how best to implement the described functionalitypresented throughout this disclosure depending on the particularapplication and the overall design constraints imposed on the overallsystem.

The processing system, or any part of the processing system, may providethe means for performing the functions recited herein. By way ofexample, one or more processing systems executing code may provide themeans for receiving a request to transmit data from a wireless node in aplurality of wireless nodes; and transmitting a multi-cast message to aset of wireless nodes in the plurality of wireless nodes to permit datatransmission. Alternatively, the code on the computer readable mediummay provide the means for performing the functions recited herein.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description is provided to enable any person skilled in theart to fully understand the full scope of the disclosure. Modificationsto the various configurations disclosed herein will be readily apparentto those skilled in the art. Thus, the claims are not intended to belimited to the various aspects of the disclosure described herein, butis to be accorded the full scope consistent with the language of claims,wherein reference to an element in the singular is not intended to mean“one and only one” unless specifically so stated, but rather “one ormore.” Unless specifically stated otherwise, the term “some” refers toone or more. A claim that recites at least one of a combination ofelements (e.g., “at least one of A, B, or C”) refers to one or more ofthe recited elements (e.g., A, or B, or C, or any combination thereof).All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. §112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.”

1. A method for scheduling uplink communication in a wireless network,comprising: receiving a first transmit request message from a firstaccess terminal that includes a request to transmit data via uplink;transmitting a poll message to a first plurality of access terminals,the poll message including a solicitation for requests to transmit datavia uplink from the first plurality of access terminals; and receivingtransmit request messages from a second plurality of access terminals ofthe first plurality.
 2. The method of claim 1, further comprising:selecting a third plurality of access terminals from the secondplurality for assignment of a first simultaneous transmit opportunitybased at least in part on the received transmit request messages; andtransmitting a first transmit start message to the third plurality ofaccess terminals, the first transmit start message indicating theassignment of the first simultaneous transmit opportunity.
 3. The methodof claim 2, further comprising: receiving data from the third pluralityof access terminals in accordance with the assignment of the firstsimultaneous transmit opportunity; and transmitting a blockacknowledgement message to each of the third plurality of accessterminals based at least in part on the received data.
 4. The method ofclaim 2, further comprising: storing an indication of a transmit requestreceived from at least one of the second plurality of access terminalsthat was not selected for the first simultaneous transmit opportunity.5. The method of claim 4, further comprising: receiving data from thethird plurality of access terminals in accordance with the assignment ofthe first simultaneous transmit opportunity; transmitting a blockacknowledgement message to each of the third plurality of accessterminals based at least in part on the received data; and transmittinga second transmit start message to a fourth plurality of accessterminals, the second transmit start message indicating an assignment ofa second simultaneous transmit opportunity for each of the fourthplurality of access terminals, the fourth plurality of access terminalsincluding the at least one of the second plurality of access terminalsnot selected for assignment of the first simultaneous transmitopportunity.
 6. The method of claim 1, wherein the poll message includesa schedule indicating when each of the first plurality of accessterminals is to respond with a transmit request message.
 7. The methodof claim 6, wherein the schedule indicates fixed points in time.
 8. Themethod of claim 6, wherein the schedule indicates a deterministicbackoff corresponding to each of the first plurality of accessterminals.
 9. The method of claim 1, wherein the poll message includes aduration field indicating a time reservation during which transmitrequest messages from the first plurality of access terminals should bereceived.
 10. The method of claim 2, wherein the poll message includes apriority class specification.
 11. The method of claim 2, wherein thefirst transmit start message includes at least one of an indication of aspatial stream assigned to each of the third plurality of accessterminals, a priority class of data permitted to be transmitted by eachof the third plurality of access terminals, a time duration for datatransmission by the third plurality of access terminals, and amodulation and coding rate assignment to each of the third plurality ofaccess terminals.
 12. The method of claim 1, wherein each of thetransmit request messages from the second plurality of access terminalsindicates an amount of data to be communicated via uplink and a priorityclass of the data.
 13. The method of claim 1, further comprising:including an access terminal in the first plurality of access terminalsbased at least in part on a response by the access terminal to aprevious poll message.
 14. The method of claim 1, further comprising:including an access terminal in the first plurality of access terminalsbased at least in part on participation of the access terminal in aprevious transmit opportunity.
 15. The method of claim 2, wherein theselecting of an access terminal for assignment of the first simultaneoustransmit opportunity is based at least in part on at least one of anamount of data to transmit reported by the access terminal, an amount ofdata in a queue of the access terminal, and a priority class associatedwith the data to transmit.
 16. A method for scheduling uplinkcommunication in a wireless network, comprising: receiving a pollmessage from an access point, the poll message including a solicitationfor a request to transmit data via uplink to the access point;determining a time to transmit a transmit request message to the accesspoint based at least in part on a schedule indicated by the pollmessage; transmitting the transmit request message at the determinedtime; and receiving a transmit start message from the access pointindicating an assignment of a first simultaneous transmit opportunity totransmit data via uplink to the access point.
 17. The method of claim16, further comprising: transmitting data via uplink to the access pointin accordance with the assignment of the first simultaneous transmitopportunity; and receiving a block acknowledgement message from theaccess point based at least in part on the transmitted data.
 18. Themethod of claim 16, wherein the schedule includes a deterministicbackoff.
 19. The method of claim 16, wherein the poll message includes apriority class specification.
 20. The method of claim 17, wherein thetransmit start message includes at least one of an indication of aspatial stream assigned for the transmitting of data via uplink, apriority class of data permitted to be transmitted via uplink, a timeduration for the transmitting of data via uplink, and a modulation andcoding rate associated with the transmitting of data via uplink.
 21. Themethod of claim 16, wherein the transmit request message indicates anamount of data to be communicated via uplink and a priority classassociated with the data.
 22. A computer-program product, comprising: acomputer-readable medium comprising: code for causing a computer toreceive a first transmit request message from a first access terminalthat includes a request to transmit data via uplink; code for causingthe computer to transmit a poll message to a first plurality of accessterminals, the poll message including a solicitation for requests totransmit data via uplink from the first plurality of access terminals;and code for causing the computer to receive transmit request messagesfrom a second plurality of access terminals of the first plurality. 23.The computer-program product of claim 22, wherein the computer-readablemedium further comprises: code for causing the computer to select athird plurality of access terminals from the second plurality forassignment of a first simultaneous transmit opportunity based at leastin part on the received transmit request messages; and code for causingthe computer to transmit a first transmit start message to the thirdplurality of access terminals indicating the assignment of the firstsimultaneous transmit opportunity.
 24. The computer-program product ofclaim 23, wherein the computer-readable medium further comprises: codefor causing the computer to receive data from the third plurality ofaccess terminals in accordance with the assignment of the firstsimultaneous transmit opportunity; and code for causing the computer totransmit a block acknowledgement message to each of the third pluralityof access terminals based at least in part on the received data.
 25. Thecomputer-program product of claim 23, wherein the computer-readablemedium further comprises: code for causing the computer to store anindication of a transmit request received from at least one of thesecond plurality of access terminals that was not selected for the firstsimultaneous transmit opportunity.
 26. The computer-program product ofclaim 22, wherein the poll message includes a deterministic backoffcorresponding to each of the first plurality of access terminals toschedule when each of the first plurality of access terminals is torespond with a transmit request message.
 27. The computer-programproduct of claim 22, wherein the poll message includes a duration fieldindicating a time reservation during which transmit request messagesfrom the first plurality of access terminals should be received.
 28. Thecomputer-program product of claim 22, wherein the poll message includesa priority class specification.
 29. The computer-program product ofclaim 23, wherein the first transmit start message includes at least oneof an indication of a spatial stream assigned to each of the thirdplurality of access terminals, a priority class of data permitted to betransmitted by each of the third plurality of access terminals, a timeduration for data transmission by the third plurality of accessterminals, and a modulation and coding rate assignment to each of thethird plurality of access terminals.
 30. The computer-program product ofclaim 22, wherein each of the transmit request messages from the secondplurality of access terminals indicates an amount of data to becommunicated via uplink and a priority class of the data.
 31. Thecomputer-program product of claim 23, wherein the selecting of an accessterminal for assignment of the first simultaneous transmit opportunityis based at least in part on at least one of an amount of data totransmit reported by the access terminal, an amount of data in a queueof the access terminal, and a priority class associated with the data totransmit.
 32. An apparatus, comprising: means for generating a pollmessage, the poll message including a solicitation for requests tosimultaneously transmit data via uplink from a first plurality of accessterminals and generating a transmit start message indicating anassignment of a simultaneous transmit opportunity to a second pluralityof access terminals; and an antenna configured to transmit the pollmessage to the first plurality of access terminals of a wireless networkand the transmit start message to the second plurality of accessterminals.
 33. The apparatus of claim 32, wherein the means is also forstoring an indication of a transmit request received from at least oneof the first plurality of access terminals that was not selected for thesimultaneous transmit opportunity.
 34. The apparatus of claim 32,wherein the poll message includes a schedule indicating when each of thefirst plurality of access terminals is to respond with a transmitrequest message.
 35. The apparatus of claim 34, wherein the scheduleindicates a deterministic backoff corresponding to each of the firstplurality of access terminals.
 36. The apparatus of claim 32, whereinthe transmit start message includes at least one of an indication of aspatial stream assigned to each of the second plurality of accessterminals, a priority class of data permitted to be transmitted by eachof the second plurality of access terminals, a time duration for datatransmission by the second plurality of access terminals, and amodulation and coding rate assignment for each of the second pluralityof access terminals.
 37. The apparatus of claim 32, wherein the meansand the antenna are elements of a wireless access point operable toprovide simultaneous access to multiple, spatially separated accessterminals.